To adapt the diff gear must be changed as the red area on the image below. It's not very difficult to achieve if we take the time and having the right tools ... There are approximately 1 mm in width to win.

Kyosho Ultima SC Parts:

There are only two things I'd like to add to the post Julien made:

First of all, after shaving the material the bearing has to extend slightly further into the casing than the ribs (aka the recess than holds the bearing needs less shaving than the ribs). If you don't do this the diff will rub slightly on the casing, even if the bearings are far enough apart (I think it has something to do with the screws that close the diff).

Also, take things slowly, it's best to shave off, test fit everything and repeat the cycle until you have enough clearance rather than overdoing it.

The diff feels very nice and smooth, it's very unusual to feel this on my TRF201! The first test will be on the 28th of July on astroturf, as a practice session for the nationals race one day later. I'm very curious about how it will drive, stay tuned!